Field of the Invention
This invention relates to waste treatment plants. More particular, the present arrangement relates to an improved cover arrangement for waste treatment plants.
Description of Related Art
A major nuisance in wastewater treatment plants around the country is the presence of algae on the surfaces of the treatment plant clarifiers. Algae grow in the presence of nutrients in the treated water and coat the surfaces of the launder trough, the weirs and scum baffles in the clarifier. Not only are the algae nuisances, but algae can build up to the point that they effect the hydraulic flow in the clarifier, they clog filters downstream and reduce the efficiency of the UV processes designed to further cleanse the outgoing water (the effluent) from the clarifier.
The most effective way to reduce algae growth in the clarifier is to cover the susceptible areas from sunlight to inhibit the growth of the algae. For this purpose, covers, usually of fiberglass, are installed over the effluent trough of a clarifier. The cover is a system of molded panels that attach to the wall of the clarifier and extend from the outer tank wall over the launder and weir and to a point inside the scum baffle thus protecting this entire area from direct sunlight and inhibiting the growth of algae on the surfaces below. The covers are hinged to allow the covers to open for inspection and maintenance. FIG. 1 shows a prior art image illustrating a typical launder channel with a cover there over and FIG. 2 shows a perspective view illustrating a plurality of covers in series, mounted around the launder channel to cover the entire channel.
Each of the cover sections in a typical prior art arrangement are made from two parts, a mounting section that attaches to either the tank wall or the weir wall of the clarifier and serves as the base for the second part, the hinged cover section that opens and closes. As shown in prior art FIG. 3, the two sections are fastened together with a continuous hinge. If the mounting section is fastened to the inner wall of the clarifier, the cover section opens toward the outer wall of the tank; if the mounting section is attached to the weir wall of the clarifier, the cover section opens toward the center of the tank.
Launder covers of this type for circular clarifier tanks are designed to follow the curvature of the clarifier wall. Typically, the outer edge of cover sections are approximately 6′ long, with the edges of the cover aligned radially inward toward the center of the tank. The mounting sections are proportionally smaller. The cover system as a whole is designed to cover the circumference of the clarifier with an even number of equal size panels to avoid the need to trim or add panels. As an example, the cover for a 100-foot diameter clarifier might normally consist of fifty four (54) individual cover sections, each 5′9⅞″ long. The mounting section would be approximately 5′ long.
Consideration must also be given to the type of cover provided. Some cover systems feature a series of identical cover panels that are spaced ¼″ to ½″ apart to allow room for a gasket between the cover panels to keep light from reaching the surface below. Other covers incorporate 3″ molded tabs at each end of alternate cover panels to extend over the seam between panels to keep out the light. A third has a molded tab at one end of the panel that allows the panels to be opened in a particular sequence. In all of these cover arrangements, both tank wall mounted and launder all mounted, the alignment of the panels and the space between panels is critical to the performance and the appearance of the cover and must be maintained.
These above prior art arrangements present a major issue with the prior art. While the cover is designed for a perfect circle, the walls of the tank and the launder wall are formed using chorded plywood forms and the result is a wall that is only approximately circular. Rather than a smooth circular surface, the cover is often mounted to a highly irregular surface of short chords. When the mounting sections are attached to this surface, it takes on a direction roughly perpendicular to the angle of the small section of the wall where it is mounted, and the attached cover sections follow suit. The adjacent sections may point in a slightly different direction causing the panel members to be mis-aligned relative to one another causing air/sunlight gaps and otherwise affecting the ability of the cover sections to open and close properly.
A second challenge to maintaining the alignment is dependent on the installation contractor. The required spacing between mounting sections is typically in the range of ¼″ to ½.″ This spacing is developed in the cover design equations and is used to ensure that the number of panels provided fits the circumference of the clarifier without the need to cut preformed panels on-site or add partial panels.